This invention relates to the art of inserting sleeves into tubing and has particular relationship to the insertion of sleeves into the primary tubing of the steam generator of a nuclear reactor plant. This invention has unique utility when integrated into the sleeving of such steam generator tubes. It is however realized that this invention has general utility and to the extent that it is employed in other areas than sleeving of steam generator tubing, such uses within the scope of equivalents of this invention.
In the operation of nuclear power plants it has been found that the primary tubes become corroded. Usually the corrosion is experienced at or near the region where the tubes emerge from the tube sheet into the mixture of water and the steam which is produces. The corrosion problem is met either by sleeving the tubes or by plugging them. The sleeves which are inserted in the tubes are typically 4 to 6 ft. long but may be much longer. In the past the practice has been to sleeve the corroded tubes inwardly from the periphery of the tube sheet. In this region there is adequate depth to manipulate the elongated hollow cylindrical member or sleeve blank which serves as a sleeve. The corroded tubes near the periphery of the tube sheet, where a straight cylindrical member cannot be readily manipulated, were plugged. The plugging has the serious drawback that there is a loss in the available power output from the plant for each plugged tube. A loss of 15% in available power has been experienced from the plugging of tubes near the periphery.
Prior to this invention consideration was given to attempting to sleeve tubes in regions of the steam generator, where the cylindrical member is too long to be manipulated, by pushing the member through a bender within the steam generator, then through a straightener and then into the tube. This approach was found not to be practicable because it demanded too high a force to be exerted on the member. The impracticability was exacerbated by the usual requirement that the sleeving be composed of the hard high nickel-chromium alloy sold under the name INCONEL. Typically the sleeving member is composed of INCONEL-600 which is sold by Huntington Alloy Products Division of International Nickel Corporation and has the following typical composition in weight percent:
Ni--72 minimum PA1 Cr--14-17 PA1 Fe--6-10 PA1 C--0.15 maximum PA1 Mn--1.0 maximum PA1 S--0.015 maximum PA1 Si--0.5 maximum PA1 Cu--0.5 maximum
It was found that under no conceivable circumstance could the tubes be sleeved by pushing a member of this material into a tube through a bender and a straightener within the steam generator.
It is an object of this invention to provide apparatus whose practice and use shall lend itself to the practicable and effective sleeving of the tubes of a steam generator, or tubes generally, particularly with sleeve blanks of hard high nickel-chromium alloys, regardless of how long the sleeve blanks are and how limited the dimensions of the region in which the blanks are to be manipulated. This object is directed not only to practicable and effective sleeving of tubes near the periphery of the tube sheet of a steam generator but to the sleeving with long blanks well within the periphery.